1. Field of the Invention
This invention relates to a leak-proof closure for a container, to a container fitted with such a closure, and to the combination thereof. More particularly, it relates to a container having a snap on, screw-off closure that is hermetically sealed against leakage.
2. Description of the Prior Art
Many containers and closures are especially designed to prevent leakage from the container. Non-leakage is of particular importance where biological specimens, such as urine specimens, are involved because leakage from one container can cross-contaminate the contents of another container and lead to mis-diagnoses and other unwanted outcomes. Urine specimen containers are particularly susceptible to cross-contamination because they are typically packed and transported in close proximity to one another and are easily tipped over or jostled. The contents of one container can easily mix with the contents of its contiguous containers if any leakage is present.
Snap-on, screw-off lids are known, but they are seldom used with biological specimen containers because they are susceptible to leakage. Moreover, since they are not hermetically sealed, they cannot be used in applications requiring the container to maintain a positive pressure or a vacuum. The conventional wisdom, therefore, is that screw-on, screw-off lids are best used in such applications.
Containers which are fitted with conventional screw caps perform satisfactorily as biological specimen containers provided that the screw caps are fitted correctly and that the thread formation is dry when the cap is screwed into position. If, however, the cap is cross-threaded or urine is present on the thread formation, leakage can occur. Leakage arising from the presence of urine on the thread formation occurs because of capillary action.
A number of leak-free screw-on lids have been developed, but the rotational-motion, automatic or robotic equipment required to screw the lids on is expensive.
There is a need, then, for a snap-on, screw-off lid that is free from leakage problems. Such a lid could be installed on containers in mass production lines by inexpensive, non-rotational, vertically-reciprocating automated equipment. Accordingly, it would benefit not only the biological specimen handling industry but the container and bottling industries in general as well. Still further benefits would accrue if such a container could be provided with hermetic sealing means.
What is needed, then, is a container and snap-on, screw-off closure design that prevents leakage of fluids even when the container is inverted or tipped over on its side. There is a need for such a container and closure design that maintains a vacuum or pressure as well.
However, at the time the present invention was made, it was not obvious to those of ordinary skill in this art how the needed structure could be provided.